Prevent site engagement scores from decaying when Chrome isn't in use.

chrome/browser/profiles/profile.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/profiles/profile.h"
 
 #include <string>
 
 #include "build/build_config.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 69 matching lines @@
       true,
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
 #if BUILDFLAG(ANDROID_JAVA_UI)
   registry->RegisterStringPref(
       prefs::kContextualSearchEnabled,
       std::string(),
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
 #endif
   registry->RegisterBooleanPref(prefs::kSessionExitedCleanly, true);
   registry->RegisterStringPref(prefs::kSessionExitType, std::string());
+  registry->RegisterInt64Pref(prefs::kSiteEngagementLastUpdateTime, 0);

[calamity, 2016/06/23 05:18:40]

This should be a lossy pref.

   registry->RegisterBooleanPref(
       prefs::kSafeBrowsingEnabled,
       true,
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   registry->RegisterBooleanPref(prefs::kSafeBrowsingExtendedReportingEnabled,
                                 false);
   registry->RegisterBooleanPref(prefs::kSafeBrowsingProceedAnywayDisabled,
                                 false);
   registry->RegisterBooleanPref(prefs::kSSLErrorOverrideAllowed, true);
   registry->RegisterDictionaryPref(prefs::kSafeBrowsingIncidentsSent);
@@ skipping 132 matching lines @@
   if (a->IsSameProfile(b))
     return false;
   return a->GetOriginalProfile() < b->GetOriginalProfile();
 }
 
 double Profile::GetDefaultZoomLevelForProfile() {
   return GetDefaultStoragePartition(this)
       ->GetHostZoomMap()
       ->GetDefaultZoomLevel();
 }